This proposal is concerned with the characterization of the transforming DNA sequences of Yaba monkey tumor pox virus. Study of the cause and effect relationship between the presence of viral DNA sequences, their expression, and the transformed state of the cells will be made using revertants to test for the presence of viral DNA sequences and using DNA from transformed cells to transform other cells. Identification of viral DNA sequences responsible for transformation will be made initially by screening independently transformed cell lines for common DNA segments and by serial transformation with viral DNA segments isolated from transformed cells on the theory that serial transformation will lead to loss of unlined, nonessential viral DNA sequences in transformed cells. The physical state of Yaba virus specific DNA in the nucleus of transformed cells will be characterized as existing free in the nucleus or integrated into the cellular DNA or both. Fine mapping of viral DNA sequences found in transformed cells will be studied by subcloning cloned DNA fragments found in transformed cells and using Northern blot hybridization and in vitro translation of identified messengers. Proteins synthesized will be compared to those in transformed cells. The role of viral DNA in the transfection of cells will be studied by neoplastic transformation of Balb/c 3T3 fragments of Yaba virus DNA will be used to identify Yaba DNA sequences in the genome of transformed cells. The possibility that the transforming DNA sequences of Yaba virus are found in other pox viruses will be investigated. Genetic expression of Yaba virus DNA sequences found in transformed cells will be studied. Cells transformed with Yaba virus will be tested for their ability to form tumors in hamsters, mice and monkeys. Characterization of the transforming DNA sequences of Yaba virus should elucidate additional information that will lead to the identification of the mechanism(s) of transformation by Yaba virus. This information is of particular interest because Yaba virus is oncogenic in monkeys, its natural host, and it produces tumors in man.